Case IH 2872-07 - BCM – BCM (Body Control Module): BCM: CAN main light switch - switch error

Case IH fault code logic for "switch errors" over a CAN (Controller Area Network) bus typically indicates an invalid signal state. This means the control module is receiving an "out of range" voltage, an open circuit, a short to ground, or conflicting switch position inputs (e.g., the switch is simultaneously registering as both ON and OFF) from the main light switch.

• MAGNUM AFS Connect
• Magnum series (e.g., 235–340 Series 4)
• Puma series
• Farmall Pro EP tractors

1. 1

   Check Fuses: Verify the power supply to the switch and BCM. For example, on Farmall Pro EP models, check fuse F-013 (15 A) which supplies the main light switch, and CAN bus fuses (e.g., 10A Mini Red fuse).

2. 2

   Inspect the Harness and Connectors: Look for intermittent pin contact, moisture damage, or corrosion on the signal traces at the main light switch connector and the BCM.

3. 3

   Test for Shorts/Opens: Trace the input/output circuits between the light switch and the BCM to ensure the wiring is not shorted to ground or shorted to a 12V/5V reference voltage.

1. 1

   Power Down

   Disconnect battery power before servicing the BCM or CAN bus circuits to prevent voltage spikes.

2. 2

   Fuse Replacement

   If the main light switch fuse (e.g., F-013) is blown, replace it and test the circuit. If it blows again, there is a short in the harness or switch.

3. 3

   Switch Replacement

   If the wiring harness tests good but the BCM still registers a "switch error" (invalid signal), remove the dash panel or control arm housing to access the main light switch and replace the physical switch.

4. 4

   BCM Repair/Replacement

   If a new switch does not resolve the CAN communication error, the BCM itself may have suffered internal damage (e.g., burned driver circuits, faulty signal conditioning ICs, or cracked solder joints). The BCM will need to be sent to a specialist for circuit-level repair or replaced entirely.

5. 5

   Calibration

   Note that installing a new controller/module on some Case IH tractors may require dealer calibration to recognize the CAN network components.